If you open the original microphone you can see two parts near the tone switch;..a resistor of 680 Ohms and a electrolyt capacitor of 0,33µF.
You get a higher audio level by removing the 680 Ohms resistor cause this is ALWAYS paralleled to the dynamic mic capsule, regardless of the position of the tone switch. On the other hand without the resistor you have to change the capacitor too to get a equal tone switch effect.
So on mine I removed the resistor and replaced the 0,33µF electrolyt with a normal keramic capacitor of 22nF (0,022µF). For my opinion all values between 22nF (0,022µF) and 100nF (0,1µF) would be ok.
Now you can notice a greater possible distance to the mic without the strong break in of the audio level. So this means the speaking distance to the stock mic can vary more without loosing too much audio level.